Re: lots of suspicious RCU traces

[Oleg Nesterov]

On 10/24, Sergey Senozhatsky wrote:
>
> small question,
>
> ptrace_notify() and forward calls are able to both indirectly and directly call schedule(),
> /* direct call from ptrace_stop()*/,
> should, in this case, rcu_user_enter() be called before tracehook_report_syscall_exit(regs, step)
> and ptrace chain?

Well, I don't really understand this magic... but why?

Until we return to user-mode this CPU should be in "in_user = false" state.

I am not sure I understand how it is guaranteed that rcu_user_exit() was
called... probably TIF_NOHZ should trigger the slow path and ensure that
syscall_trace_enter()->rcu_user_exit() will be called.

Oleg.

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